Hi Yanick, I don't know it by hard the healthy level of magnesium but I would suggest to look it up via the World Heatlh Organisation (WHO). The have standards for save drinking water, these are international but it can differ locally/national. For instance I know that the drinking water standards in The Netherlands are more strict then the ones of the WHO.

Hi Jeroen, i thank you for your answer. I didn't find anything about the threshold value of magnesium in drinking water via the World Health Organization. I know that drinking water is the main source of supply of minerals and magnesium is essential for good health particularly for the cardiovascular physiology. The literature reports an association between low magnesium concentration in drinking water and mortality from cardiovascular disease (Schroeder, 1960; Sharret, 1979; Masironi et shaper, 1981). I think it should have a threshold value of magnesium in drinking water.

you can consult the books of medical geology r water hardness in the chapter Rubenowitz - Lundin E., M. Hiscock K (2005). Water Hardness and Health Effects. IN: Selinus O, Alloway J. B., A. Centeno J. B. Finkelman R., R. Fuge, U. Lindh, P. Smedley Essentials of Medical Geology. London: Elsevier Academic Press, p. 331-345. ISBN: 0-12-636341-2.

I would suggest to look it up via the World Health Organisation (WHO) or "EPA Gold book". The have standards for save drinking water, these are international but it can differ locally/national.

Thanks a lot. I consult the book and I look it up via the World Health Organization also. I've read that the threshold value of water hardness ranges between 60 mg/L and 150 mg/L to overcome the entartrages pipes and its ability to react with soap. No health-based guideline value for water hardness is proposed (WHO, 1996). Indeed, An inverse relationship between the water hardness in drinking water and mortality from cardiovascular disease has been reported. Several studies have shown that the mortality from cardiovascular disease is higher where the magnesium concentration in drinking water is less than 7 mg / L.

Hi Yanick i would like know the expostion time with a water hardness to develop heart desease.

Hi Yanick, Magnesium is a cation which allows to control acidification. In water, it is only retained in hardness concentration. Since hardness is not considered until today as a toxic substance for human health, the necessity to determine a threshold value in drinking water, particularly for its two main components (Calcium and Magnesium), is not constituted an object of research. However, different studies show a correlation between hardness and cardivascular diseases. In the reference recommanded by Cajouste there is a very interesting chapter on this issue.

I am pleased to send a link and the french version of European standards of water (1998)

http://www.epa.gov/safewater/contaminants

Dear Yanick, I think that the attached article would help you in your work.

the Magnesuim and calcuim ions are both contrubue the hardness water there in so much literature. you can consult the book of medical geology in his chapter that treat hardness water. according to the literature magnesium concentration lower than 7 mg / l and concentration of calcuim superior to 200 in drinking water is considered hard water, which can lead to cardiovascular problem

Thanks a lot for your answers. I really appreciate the last document you have sent. It reviews the strengths and weaknesses of the epidemiologic evidence relating magnesium to the three stages of the natural history of ischemic heart disease (IHD). It reviews also the substantial biologic evidence suggesting that magnesium could affect smooth muscle and cardiac muscle irritability, impulse transmission and other physiologic processes which are disrupted in persons with IHD. The autopsy studies of myocardial magnesium concentrations by Sharrett and Esenberg are very interesting. They found that decedents who died from IHD had significantly lower magnesium levels in heart muscle and diaphragm muscle than did decedents who died from accidents.

I will be very pleased to receive other documents which can help me with my work.

In case there would be no threshold effects could there be a derivative with minimum dose effect expressing a reference level of risk considered negligible in the characterization of the hardness of the water and cardiovascular disease?

In my opinion, the question of the toxicological effects of water hardness on human health must be approached from the basis of cumulative risk assessment or study the combined effects of substances causing water hardness . In this context, it seems pertienent guide especially the reflection on the study of interactions between calcium and magnesium.

Given the strong presence of the limestone in the geology of Haiti and its important contribution to hardness of the water resources of this country, I would be very interested to start with you, Yanick, from September 2014 a PhD thesis on the issue of water hardness and cardiovascular diseases.

As part of the implementation of this thesis, you could possibly study the combined effects of limestone and magnesium in rats or mice. Thank you for keeping me informed of your response, favorable or not, on my proposal.

Thanks a lot for your answer Professor Emmanuel. The study of interactions between calcium and magnesium is very necessary. Magnesium is antagonist of calcium and calcium had possibility to interfere magnesium’s absorption with high value.

Dear Professor Emmanuel

I am very pleased to receive this message. I will be extremely glad to start with you a PhD thesis from September 2014 on the issue of water hardness and cardiovascular diseases. It will be very interesting to study the combined effects of limestone and magnesium in rats.

Hi yanick the last week i read on your publication that you mentionned two kinds of water hardness . according of your publication you considere a water as hardness if the concentration of calcuim is upper than 200 ppm and magnesuim less than 7ppm that can be provoke lithiasis and may be cardiovascular desease the other with a concentration of calcuim upper 200 ppm and a concentration of magnesuim upper than 10ppm and you are not mentionned for the last what type of problem it's can be provoke in the human body.

Water hardness > 200 mg/L can cause entartages pipes even though magnesium is low or not. The entartages’ result can promote bacterial overgrowths which constitute a danger to consumers.

According to prompt of WHO that the threshold value of magnesium in drinking water is minimum 10mg / l and the optimum of 20-30 mg / l, while Calcium is minimum 20 mg / l 0ptimum ranges from 50 (40-80) mg / l. Then the amount of calcium and magnesium: 2 to 4 mmol / l

Standard guideline value: According to WHO 2011 there is not guideline value for Mn is suggested. This is mainly because the level in which Mn present in water is not posing any health problems.

Regional threshold value is the natural background value of Mn (can be derived from Cumulative probability plots of the bulk amount of data). If the concentration exceeds the Regional threshold value that sample may be consider as contaminated.

Thank you for your answers.

Water hardness has significant effect on heavy metals toxicity such as Cd, Hg, Ni, Pb, Cu, Co and Zn. These metals tend to increase in soft water. For a long time, it has been known that most heavy metals become less toxic in water hardness (Taylor et al., 2000).

Does anybody knows why heavy metals become less toxic in water hardness?

The maximum permissible limit of Mg in drinking water is